1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to elevator systems which use a notching type floor selector.
2. Description of the Prior Art
While the floor selectors of many elevator systems are now of the solid state type, a large number of the slower speed elevator systems still utilize notching type floor selectors which develop notching signals as the elevator car travels through the hoistway. These notching signals update the floor selector by picking up and dropping out certain electromechanical relays. The energized relay indicates the exact position of the elevator car in the hoistway when it is standing stationary at a floor of the associated building, and it indicates the next floor at which the moving elevator car can make a normal stop. Each time the moving elevator car notches into the next floor, the new floor registered or stored in selector is compared with the registered calls for elevator service. Thus, when the floor selector notches into a relay associated with a floor for which there is a call for service, appropriate preparation for slowdown and stopping at this floor is initiated.
If the electrical power to the floor selector should be interrupted, or the floor selector gets out of step with the actual car position for any other reason, the operation of the elevator car will be incorrect, degrading the level of service. Thus, it is common to employ an initialization procedure following power turn-on which involves causing the elevator car to travel in a predetermined direction to a terminal floor, with the floor selector then being set to correspond to this terminal floor. If the floor selector should get out of step for a reason other than power failure it will also be corrected at a terminal floor, as it is common to reset the floor selector each time the elevator car arrives at a terminal floor. Other prior art arrangements utilize such expedients as coded indicia in the hoistway at each floor and appropriate "readers" of the indicia on the elevator car; or, batteries for powering car position memory circuits during a power outage.
It would be desirable to be able to monitor and correctly reset an out-of-step notching floor selector without requiring the elevator car to move to a predetermined reset floor, without requiring coded indicia in the hoistway and code readers on the car, and without requiring batteries of other auxiliary power supplies.